Roller for supporting and/or driving flat products, comprising a sensor

ABSTRACT

A roller comprises a thermocouple delivering a voltage signal which is converted by converting mechanism carried by the roller into a stabilized signal whose magnitude is independent of the resistance of the output circuit. The stabilized signal is transmitted to the fixed part of the measuring circuit by a device comprising slip rings and fixed collectors. The converting mechanisms are disposed in a case of the roller and provided with an air cooling device. The air is channelled in the case by annular supports and frames carrying the converting mechanism. Application in the measurement of the temperature of flat products travelling through a continuous annealing furnace.

The present invention relates to a roller for supporting and/or drivingflat products or sheets comprising one or more temperature sensorsconstituted by thermocouples.

In the course of the manufacture of the sheet, the state of the latteris monitored by carrying out various measurements, for exampletemperature measurements.

It is known to carry out these measurements by incorporating at leastone thermocouple in a roller supporting or driving the sheet.

To transmit the signal directly from the thermocouple to a fixedmeasuring apparatus located outside the roller, it is not possible toemploy systems comprising slip rings and collectors. Indeed, this signaldelivered by the thermocouple is a voltage of low value, of the order ofa millivolt, and if one tried to transmit this signal through a set ofrings and collectors, the signal would be excessively disturbed byelectric pollutants created by the environment and variations inresistance in the circuit due to imperfect contacts between the sliprings and the collectors. The resulting measurement would totally lackprecision.

DISCUSSION OF THE RELATED ART

In order to solve this problem, it has already been proposed, forexample in the document U.S. Pat. No. 3,824,857, to convert in therotating part the millivolt signal issuing from the thermocouple into asignal modulated in frequency and to transmit this frequency-modulatedsignal to the fixed part through rotating transformers or radio wave.

However, these systems are sophisticated and expensive and are notcompletely protected against possible exterior disturbances of thesignal.

SUMMARY OF THE INVENTION

An object of the invention is to transmit to the fixed part of themeasuring circuit a precise signal insensitive to electric pollutants,by employing simple and consequently inexpensive means.

The invention therefore provides for a roller for supporting and/ordriving flat products or sheets including at least one thermocouple,characterized in that the roller comprises converting means constituted,for each thermocouple, by a converter converting the voltage signaldelivered by the thermocouple into a stabilized current whose value isindependent of the resistance of the circuit in which this currentflows, and a set of slip rings and fixed collectors the rings of whichare connected to the outputs of the converters.

With the device according to the invention, the signal recovered on thefixed collectors and transmitted to the measuring circuit which is fixedwith respect to the roller, is a current signal of a plurality ofmilliamps whose value is independent of the disturbances produced by therings-collectors system and precisely reflects the voltage signaldelivered by the thermocouple.

According to other features of the invention:

a connector is interposed between each thermocouple and the associatedconverter;

the roller includes air cooling means for the converting means;

the converting means are disposed inside a case and said cooling meanscomprise a cooling air inlet port provided in the wall of the case, andannular supports and frames in the vicinity of the axis of which theconverting means are fixed, which define a path for the circulation ofthe air in the case.

The invention is also applied to a roller comprising a hollowcylindrical body whose outer surface cooperates by contact with thesheet, and at least one thermocouple disposed inside the cylindricalbody and having one end or hot junction disposed in the wall of thecylindrical body in the vicinity of the outer surface of the latter,characterized in that the thermocouple is removably passed through aguide tube which extends inside the hollow cylindrical body and has anend opening onto a blind hole in the wall of the cylindrical bodyconstituting a cavity for the hot junction.

According to other features of this roller:

the end of the guide tube through which the hot junction extends isfixed to the inner surface of the cylindrical body by a connector whosefirst end or base is soldered to the inner surface of the cylindricalbody and whose second end or spigot is soldered to the guide tube;

the characteristics of expansion of the material of the connector aresubstantially equivalent to those of the material of the cylindricalbody;

the end of the guide tube through which the hot junction extends and theblind hole forming a cavity for the hot junction are substantiallyperpendicular to the wall of the hollow cylindrical body;

the guide tube is mounted with clearance, inside the roller, in supportsand staples connected to the roller, and

sealing means seal off the gases contained in the hollow cylindricalbody from the converting means.

The invention also provides an annealing furnace for the continuoustreatment of flat products or sheets employing at least one rolleraccording to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described hereinafter withreference to the accompanying drawings in which:

FIG. 1 is a partial diagrammatic longitudinal sectional view of asheet-driving roller;

FIG. 2 is a detail sectional view of the part of FIG. 1 delimited bydot-dash lines and designated by the reference numeral 2;

FIG. 3 is a detail view of FIG. 1 showing a first support of a guidetube;

FIG. 4 is a sectional view taken on line 4--4 of FIG. 3;

FIG. 5 is a detail view of FIG. 1 showing a second support of the guidetube;

FIG. 6 is a sectional view taken on line 6--6 of FIG. 5;

FIG. 7 is a cross-sectional view of the guide tube disposed in a staple;

FIG. 8 is a cross-sectional view of the guide tube disposed in a supportand a staple; and,

FIG. 9 a partial longitudinal sectional view of an electromechanicaldevice disposed at one end of the roller.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a sheet-driving roller 10 employed in an annealing furnaceof a continuous treatment installation. This roller 10 comprises ahollow cylindrical body 12 including a straight cylinder 14 havingopposite ends respectively closed by two plugs 16 defining a neck. Owingto the symmetry arrangement, only one of the plugs 16 is shown, namelythat placed at the right end of the cylinder 14 as viewed in FIG. 1. Thecylinder 14 has, in the presently-described embodiment, a length of1,800 mm, a diameter of 600 mm and a wall 20 mm thick. The outer surfaceof the wall of the cylinder cooperates with the sheet by contact. Theplugs 16 are respectively welded to each end of the cylinder 14 in theregion of their largest diameter and comprise a shaft 18 which ismounted in the end of the respective plug 16 in the region of thesmallest diameter of the plug. The plugs 16 extend through a wall 20defining the enclosure of the furnace. The bearings carrying the shafts18 and the means for controlling and driving the roller are locatedoutside the furnace and are not shown in the Figures. Ports 22 extendingin a direction roughly perpendicular to the walls of each plug put theinterior of the hollow cylinder 12 in communication with the atmosphereof the furnace for homogenizing the hot gases in the roller 10 and inthe furnace.

The shaft 18 shown in FIG. 1 is stepped and defines cylindrical portionswhose diameters decrease in the direction of the free end of the shaft.The free end of the shaft includes a stepped axial bore 24 and anelectromechanical device which is shown in FIG. 9 and will be describedhereinafter.

Extending through the shaft 18 on the axis of the latter is a conduit 26in which is partly disposed a guide tube 28 adapted to receive atemperature sensor, namely a thermocouple. The guide tube 28 extendsfrom the stepped bore 24 of the shaft 18 to the wall of the cylindricalbody 12 where it is fixed roughly in the region of the median transverseplane 30 of the roller shown in dot-dash lines in FIG. 1. In thepresently-described embodiment, the guide tube 28 is of stainless steel.It has a diameter of 6 mm and its wall has a thickness of 1 mm. Themeans for positioning the guide tube inside the cylindrical body 12 willbe described in more detail hereinafter.

FIG. 2 shows how the end of the guide tube 28 is fixed to beperpendicular to the wall of the cylindrical body 12 by a connector 32.This connector has a generally cylindrical shape and consists of twocylindrical portions 34, 36, one of which is of large diameter and istermed a base 34 welded to the inner surface of the cylindrical body 12,whereas the other is of small diameter and is termed a spigot 36 whichis welded to the guide tube 28. The connector 32 is preferably composedof a material having the same coefficient of expansion as the wall ofthe cylindrical body 12 so as to optimize the strength of the fixing ofthis connector to the wall of the cylindrical body 12 and avoid in thiswall the creation of stresses which would otherwise result fromdifferential expansions.

The end of the guide tube 28 extends through the connector 32 and opensonto a blind hole 38 provided in the wall of the cylindrical body 12 ina position perpendicular to this wall. In the illustrated embodiment,the inner end of the blind hole 38 is at 3 mm from the outer surface ofthe cylindrical body 12. However, this distance may be reduced to 1 mmby employing an apparatus capable of precisely measuring thickness forthe machining of the blind hole. With reference to FIG. 2, it can beseen that the upper end of the blind hole 38 has an inside diameteradapted to receive the end of the guide tube 28, and the lower end ofthe blind hole has a smaller inside diameter less than the diameter ofthe guide tube 28 and is adapted to receive the end of a thermocouple 39constituting the hot junction. A shoulder 40 which constitutes theboundary between the two parts of the blind hole 38 whose insidediameters are different has a rounded shape to facilitate placing theend of the thermocouple in position in the inner end of the blind hole38 and avoid initiating any fracture.

FIGS. 3 to 8 show in more detail the mounting of the guide tube insidethe roller 10. FIG. 3 shows how the guide tube 28 is positioned in thecylindrical body 12 by means of a first support 42 in the form of aplate. This support 42 is disposed in a longitudinal plane of the hollowcylindrical body 12 and is fixed by a longitudinal edge to the innersurface of the hollow cylindrical body 12. A groove 44 is provided inthe free edge of the support 42. The section of the groove 44 is shownin FIG. 4. The width and depth of the groove 44 are adapted to receivethe guide tube 28 with clearance. The contour of the edge of the support42 in which the groove 44 is provided defines curved shapes which givepredetermined orientations to the guide tube 28. Thus, as viewed in FIG.3, the end of the guide tube extends out of the groove 44 on the leftside of the support 42 in a direction perpendicular to the wall of thecylindrical body 12. Likewise, the guide tube 28 extends out of thegroove 44 on the right side of the support 42 in a direction roughlyparallel to the wall of the cylindrical body 12.

Shown in FIG. 5 is a second support 46 for the guide tube 28, in theform of a plate which is contained, as the foregoing plate, in alongitudinal plane of the cylindrical body 12. This support 46 is fixedby an edge to the inner surface of the plug 16 of the cylindrical body12. As for the previously-described support 44, a groove 48 is providedin the free edge of the support 46. The section of the groove 48 isshown in FIG. 6. The contour of the edge of the support 46 definescurved shapes whereby predetermined orientations may be given to theguide tube 28 which is received in the groove 48 without clearance.Thus, with reference to FIG. 5, although the guide tube 28 is not shownin this Figure, it will be understood that, on the left side of thesupport 46, the guide tube 28 extends out of the groove 48 and isroughly parallel to the wall of the cylindrical body 12, and, on theright side of the support 46, the guide tube 28 extends out of thegroove 48 and is roughly on the axis of the conduit 26 of the shaft 18.

As already seen in FIG. 1, the guide tube 28 extends between the twosupports 42, 46 alongside the wall of the cylindrical body 12. FIG. 7shows one of the staples 50, termed short-branch staples, maintainingthe guide tube 28 against the wall of the cylindrical body 12 betweenthe two supports 42, 46. These staples 50 are fixed to the inner surfaceof the wall of the cylindrical body 12 by welding. The guide tube 28 ismaintained closely between the staple 50 and the inner surface of thewall of the cylindrical body 12.

Shown in FIG. 8 is one of the staples 52, termed long-branch staples,disposed in a transverse position with respect to the groove 44 of thesupport 42. Long-branch staples 52 are also disposed on the support 46in a manner similar to that shown in FIG. 8. It can be seen that, indistinction to the short-branch staples 50 shown in FIG. 7, thelong-branch staples 52 maintain the guide tube 28 in the groove 44 withclearance. The guide tube 28 is therefore maintained with clearancebetween the walls of the grooves 44, 48 and the staples 52 to permitsmall displacements of the guide tube due to its expansion.

The thermocouple is disposed inside the roller 10 by passing it throughthe guide tube 28 when the roller has been placed in position in thefurnace. However, the machining of the blind hole 38 where the hotjunction of the thermocouple is received, and the fixing of the guidetube 28 inside the cylindrical body 12 must be carried out before fixingtogether the various elements constituting the roller 10, in particularthe straight cylinder 14, the end plugs 16 and the shafts 18.

Only a single guide tube 28 is shown in the roller 10 in the Figures.However, it will be clear that other guide tubes 28 for thermocouplesmay also be placed in a similar manner in the roller 10. Preferably,three thermocouples are placed in the roller 10 and disposedrespectively in three guide tubes 28. This permits dynamically balancingthe roller 10 which is driven in rotation. The hot junctions of thethermocouples are for example disposed in the median transverse plane ofthe roller 10. However, they may also be disposed at any point of thewall of the roller.

When the roller 10 has been placed in position in the furnace, thethermocouple is passed through the guide tube 28 at the end of thelatter which opens onto the stepped bore 24 of the shaft 18. The body ofthe thermocouple is urged so as to place the hot junction in position atthe inner end of the blind hole 38 of the wall of the roller, at theother end of the guide tube 28.

FIG. 9 shows the end of the shaft 18 on which there is fixed anelectromechanical device 54 connected to the thermocouple. The device 54is disposed inside a case 56 fixed by screws 58 to a cover 60 connectedto a fixed bearing (not shown) carrying the shaft 18. The end of thisshaft 18 extends through the cover 60 in the region of an axial opening62 in this cover. A wearing ring 64 is fitted on the end of the shaft 18in the region of the opening 62 of the cover 60. A lip sealing element65 provides a seal between the wearing ring 64 and the cover 60.

FIG. 9 shows a single guide tube 28 extending out of the conduit 26 inthe stepped bore 24 and a single thermocouple 39 disposed in the guidetube 28. The thermocouple 39 is for example of the Chromel Alumel type.As already mentioned, preferably three thermocouples and therefore threeguide tubes 28 are provided in the roller 10. They are assembled in amanner similar to that described hereinbefore.

As already seen in FIG. 1, the conduit 26 puts the interior of thehollow cylinder 12 in communication with the stepped bore 24.Consequently, the hot gases which are inside the cylindrical body 12 canreach the stepped bore 24 via the conduit 26. Sealing means 67 seal offthe electromechanical device 54 from the hot gases contained in thefurnace and the roller 10. These sealing means 67 comprise an annularspacer member 68 disposed in the stepped bore 24, an O-ring seal 70located between the inner end of the stepped bore 24 and a first end ofthe spacer member 68, and a sealing disc 72 disposed between the secondend of the spacer member 68 and a clamping nut 74 screwed in the steppedbore 24. The thermocouple 39 is passed through an adjustable connector76 extending through the sealing disc 72. The thermocouple 39 is jammedin the connector 76 which thus maintains it in a position extending intothe guide tube 28.

The electromechanical device 54 will now be described. This devicecomprises an assembly of annular supports 78, 79, 80 which are injuxtaposed relation and fixed to the shaft 18 by screws. The supports78, 79 close to the shaft 18 respectively comprise two complementaryelements 82, 84 of a miniature connector 85, for example of the typemanufactured by the first. Thermo Electric under the reference CNN-21200.KX. The connector element 82 is connected to the thermocouple 39.The connector element 84 is connected to means for converting the signaldelivered by the thermocouple, namely a converter 86. The function ofthe converter 86 will be subsequently explained. It can be seen in FIG.9 that the electromechanical device 54 includes two other identicalconverters 86 for two other thermocouples, the electric connecting wiresand the corresponding connectors of which have not been shown. The threeconverters 86 are respectively disposed on annular frames 87, 88, 89fixed to the support 79 by screws. The converters 86 are placed on theaxis of the annular frames.

The output of the converters 86 is connected to a device 90 comprisingslip rings 91 and collectors or brushes 92 of known type. The rings 91are fixed to the support 80 which is secured to the shaft 18. Thecollectors 92, only one of which is shown in FIG. 9, are fixed to asupport 94 carried by ball bearings 96 arranged between the support 94and the ring support 80. The collector support 94 is prevented fromrotating by a screw 98 which is screwed into the latter and has a stemportion extending through an oblong slot 100 in the case 56. This slot100 allows the fixing screw 98 to travel in a direction parallel to theaxis of the roller 10 as a result of expansion of the latter.

The converters 86 convert the voltage signals (0 to 18 mV) delivered bythe thermocouples, before their transmission through the ring andcollector device 90, into stabilized currents whose magnitude is solelydependent on the magnitudes of said voltages and are consequentlyindependent of any variations in resistance (line resistances or contactresistances) of the output circuits of the converters. In thepresently-described embodiment, the outputs of the converters deliver acurrent of between 4 and 20 mA linearly corresponding to temperatures of0° to 1,000° C. In this way, the output current of the converters isinsensitive to electric pollutants created by the contacts between therings and the collectors. The ring-collector devices may consequently beof ordinary construction with no necessity to use an assembly ofsophisticated and consequently costly collectors. Precise temperaturemeasurements are in this way obtained. Further, the outputs of theconverters at 4 to 20 mA are standardized and consequently datadelivered by the thermocouples can be sent to a standard systemreceiving and processing numerical data for regulating the furnace. Themeasured signal can be directly utilized at the output of the set ofcollectors or can be sent through a single telephone line, with no otherelectronic processing, to a plurality of receivers, if need be, and at agreat distance.

Owing to the use of the connector 85 connected to each thermocouple 39,the assembly comprising the converters 86 and the ring and collectordevice 90 is easily dismantled without having to move the thermocouples39 relative to the roller 10.

The means for cooling the electromechanical device 54, in particular theconverters 86 whose operation requires moderate temperatures, will nowbe described. A port 102 provided in the case 56 in the vicinity of theend of the shaft 18 provides a cooling air inlet. The air is brought tothis air inlet port 102 by a supply device of known type (not shown inthe drawing). In the case 56, the air is channelled by an annularsealing element 104 disposed between the support 78 and the case 56, toa radial duct 106 provided in the connector support 78. The annularshapes of the supports 78, 79, 80 and the converter frames 87, 88, 89ensure a circulation of cooling air in a substantially axial path in thecase 56. The cooling of the converters 86 optimized by throughwayaxially extending passages 108 provided in the converters.

To replace a thermocouple, it is sufficient to dismantle the case 56 andthe electromechanical device 54, then extract the thermocouple bypulling on the latter at the connector 76. Another thermocouple can beplaced in position by passing the latter through the connector 76 andthrough the guide tube 28 one end of which is in the vicinity of theconnector 76.

Further, the converting means may be incorporated in any type of rollerwhich carries or drives the sheet during a sheet manufacturing process.These rollers may be disposed in some place other than the annealingfurnace, for example upstream or downstream of the latter with respectto the direction of travel of the flat product in the productmanufacturing process.

What is claimed is:
 1. A roller for supporting and/or driving flatproducts or sheets comprising at least one thermocouple, and convertingmeans carried by the roller, comprising, for said at least onethermocouple, a converter converting a voltage signal delivered by saidat least one thermocouple into a stabilized current whose magnitude isindependent of the resistance of a circuit in which said current flows,and a set of slip rings and fixed collectors, the rings of said setbeing connected to outputs of said converter so that the stabilizedcurrent flows in said set of slip rings and fixed collectors.
 2. Theroller according to claim 1, wherein a connector is interposed betweensaid at least one thermocouple and said converting means.
 3. The rolleraccording to claim 1, wherein said roller comprises air cooling meansfor said converting means.
 4. The roller according to claim 3,comprising a case for said converting means, said cooling meanscomprising a cooling air supply port provided in a wall of said case,and annular frames and supports, in the vicinity of an axis of whichsaid frames and supports said converting means are fixed, said framesand supports defining an air circulating path in said case.
 5. Theroller according to claim 1, comprising a hollow cylindrical body havingan outer wall defining an inner surface and an outer surface which iscooperative by contact with said product or sheet, at least one sensorwhich is said at least one thermocouple disposed inside said cylindricalbody, and sealing means for sealing off gases contained in said hollowcylindrical body from said converting means.